Living body photometric device

ABSTRACT

By making use of a set of loading of stimulation and no loading, variation signals in time of hemoglobin density at a plurality of measurement points of a subject attached of an optical measurement probe and corresponding to a plurality of channels are detected, and for the respective detected hemoglobin variation signals principal component analysis is performed as well as a representative signal having a higher contribution rate is extracted and the extracted representative signal is displayed on a monitor. A correlation between the representative signal and a task reference and response waveform representing a response pattern of a living body in response to a stimulation task is calculated, and a representative signal having the highest correlation value as calculated is displayed in a discriminable manner from the other signals as a task related signal which responds most to the stimulation given to the subject. From weights of the respective channels for the representative signal displayed as the task related signal, an optical measurement point or region, which responds most to the task is identified and displayed in discriminable manner.

FIELD OF THE INVENTION

The present invention relates to a living body photometric apparatus,which measures information inside a living body by making use of lightbeams and more specifically, relates to a living body photometricapparatus, which can specify accurately and easily a reactive portioninside the living body when a task load is given to the living body.

CONVENTIONAL ART

A living body photometric apparatus is an apparatus in which light beamshaving wavelength from visible region to infrared region are irradiatedto a living body and reflected or scattered light beams inside theliving body are detected so as to measure information inside the livingbody, and with which blood circulation and blood circulation dynamicsinside the living body, moreover, variation in time of light absorptionmaterials in blood such as hemoglobin can be easily measured with lessrestriction to a subject and without giving any harms to the subject.Thus clinical application of the living body photometric apparatus isexpected.

In the living body photometric apparatus, the measurement result isdisplayed such as in a graph representing hemoglobin density variationin time at a measurement position (time course representation) and in acontour imaging (topography) of a spatial distribution variation ofhemoglobin at a measurement region. Further, the measurement result isdisplayed as an image in a color phase such as red and blue assigned tospatial distribution of hemoglobin and variation in time thereof.

Examples of clinical applications of the living body photometricapparatus are such as local focus identification of epilepsy andlanguage area region identification examination as presurgicalexamination of epilepsy therapy. The language area region identificationexamination is a very important examination suppressing damage low forbrain function tissue at the time when removing the local focus portionof epilepsy and is required to correctly specify the region.

The language area region identification examination by making use of theliving body photometric apparatus is, for example, disclosed in E.Watanabe et al., “Non-invasive assessment of language dominance withnear-infrared spectroscopic mapping” Neuroscience Letters 256 (1998)49-52, in which hemoglobin variation signals are measured from aplurality of positions for each of the right and left temporal lobeswhile giving a subject language stimulus loads, the obtained pluralityof hemoglobin variation signals are added and averaged for every rightand left temporal lobes and through comparison of these averaged valuesthe language area region is identified.

Further, such as the present applicants are now developing a living bodyphotometric apparatus, which improves convenience in living bodyphotometry and objectivity in measurement and is suitable for thelanguage area region identification (see JP 11-311599 A and WO 02/32317A1)

As has been explained above, for identification of an active region inthe brain such as the language area region identification, it isimportant to diagnose a correct position thereof, and the living bodyphotometric apparatus is required to provide correct information andinformation facilitating diagnosis.

However, when performing examination for specifying the small languagearea region of about 3 cm×3 cm, since in the hemoglobin variationsignals measured other signals than activation signals in the brainbrought about by a load for the language area region identification, forexample, signals due to hand motion for writing letters and further,signals due to such as the sense of sight and the sense of hearing arecontained, the diagnosis accuracy of the method of specifying the activeportion brought about by the loading through average value comparison ofthe signals of right and left temporal lobes is not high and remains inabout 60%. For this reason, in the region specifying examination bymaking use of the living body photometric apparatus, the apparatus isdesired to be able to specify a small region as well as to be able toimprove diagnosis accuracy.

Further, with the conventional display method in the living bodyphotometric apparatus such as the time course representation ofhemoglobin variation signals for every measurement channel and thetopography representation, it was sometimes difficult to easily grasp aspecific active region.

Accordingly, an object of the present invention is to provide a livingbody photometric apparatus, which can accurately specify an objectivesmall active region in a brain from hemoglobin variation signalsmeasured.

SUMMARY OF THE INVENTION

In order to achieve the above object, the present invention ischaracterized in that a signal processing portion of the living bodyphotometric apparatus is added of a function, which performs a principalcomponent analysis for signals measured. The principal componentanalysis function is understood to be able to extract from the signalsmeasured only signals corresponding to the loaded task. Thereby, anapparatus, which permits to effectively compare interregional signalintensity and to accurately identify an active portion in the brain in aclinical examination application such as the language area regionidentification.

Namely, the living body photometric apparatus according to the presentinvention comprises a light measurement portion which measures intensityof passing light at a plurality of measurement points of a subject andoutputs signals corresponding to intensity of passing light for everymeasurement point as measurement data for every measurement channel, asignal processing portion which processes the measurement data outputfrom the light measurement portion and images a living body reactionwhen a predetermined task is given to the subject and an input andoutput portion which displays a processed result of the signalprocessing portion as well as sends a command necessary for a processingin the signal processing portion, characterized in that the signalprocessing portion includes means for performing a principal componentanalysis for the measurement data and for extracting a representativesignal which most reflects the living body reaction when the task isgiven.

Specifically, the signal processing portion performs a principalcomponent analysis for the measured data, calculates not less than onerepresentative signal and weight of the representative signal for everymeasurement channel, correlates the representative signal with areferential response signal representing a passing light pattern whenthe task is given and extracts a representative signal reflecting mostthe living body reaction when the task is given among the representativesignals as a task related signal.

According to the living body photometric apparatus of the presentinvention, since the representative signal reflecting most of the livingbody reaction when the task is given can be extracted as the taskrelated signal, through comparison of the weight of the task relatedsignal for every measurement channel, namely comparison of abundancefrequency, an active portion which reacts most with respect to the task(language area when the task is language stimulus) can be accuratelyspecified.

The present invention further provides a living body photometricapparatus with an improved display function. Namely, the living bodyphotometric apparatus according to the present invention ischaracterized in that the input and output portion is adapted to displaya waveform of the representative signal calculated through the principalcomponent analysis in the signal processing portion and the weight ofthe representative signal for every measurement channel. Further, theliving body photometric apparatus according to the present invention ischaracterized in that the calculated result of the correlation betweenthe representative signal and the referential response signal isdisplayed together with the waveform of the representative signal.

According to the present living body photometric apparatus, from ascreen on which the waveform of the representative signal is displayed,a user can discriminate among the representative signals the taskrelated signal which is a representative signal showing the highestcorrelation with the referential response signal, and further, from theweight of the task related signal for each measurement channel, the usercan discriminate a most reactive portion (a concerned measurementchannel) to the task.

In a further preferable living body photometric apparatus according tothe present invention, the signal processing portion receives acondition for the task from the input and output portion and prepares areferential response signal depending on the condition. According to thepresent living body photometric apparatus, since a referential responsesignal of a suitable reaction pattern depending on the task can be used,correctness when extracting the task related signal is improved.

In a still further preferable living body photometric apparatusaccording to the present invention, the signal processing portiondivides the measurement channels into a plurality of groups, calculatesaverage values of the weights of each measurement channel for everygroups with respect to the representative signal selected as the taskrelated signal and further calculates from the average values dominanceof the response with regard to the task in the groups thereby to displaythe same.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a schematic entire structure of aliving body photometric apparatus according to the present invention;

FIG. 2 is a flowchart of language area region identification diagnosisperformed by the living body photometric apparatus according to thepresent invention;

FIG. 3 is a view showing an attachment state of a probe to a subjectwhen the measurement object is a head;

FIG. 4 is a view showing an example in which a measurement result ofhemoglobin variation signal in response to a language stimulus loadingis displayed on a screen;

FIG. 5 is a view for explaining a principal component analysis performedfor hemoglobin variation signal measured;

FIG. 6 is a view showing an example in which a result of the principalcomponent analysis for the hemoglobin variation signal is displayed onthe screen;

FIG. 7 is a view showing an example of a screen for preparing areferential response signal which is used for analyzing the hemoglobinvariation signal; and

FIG. 8 is a flowchart of dominance hemisphere identification performedby the living body photometric apparatus according to the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENT

Herein below an embodiment of the present invention will be explained indetail. In the explanation below, as an object of light measurement,amount of hemoglobin (including oxy hemoglobin, deoxy hemoglobin andtotal hemoglobin) in a living body is referred to, however, in theliving body photometric apparatus according to the present invention,substances such as cytochrome other that the hemoglobin which absorblight beams of near infrared region can be used as the measurementobject.

FIG. 1 is a block diagram showing a schematic entire structure of aliving body photometric apparatus according to the present invention.The living body photometric apparatus is provided with a light source 10which irradiates near infrared light beams to a living body, an opticalmeasurement portion 20 which measures light passed through the livingbody and converts the same into an electrical signal and a signalprocessing portion 30 which calculates living body information, morespecifically, hemoglobin density variation in blood at a measurementportion based on the signals from the optical measurement portion 20 anddisplays the result. Further, in order to contact an end of an opticalfiber to a measurement position of a subject for transmitting lightbeams from the light source 10 as well as to contact an end of anotheroptical fiber to a measurement position of the subject for detectinglight beams passed (including scattered) inside the living body and fortransmitting the same to the optical measurement portion 20, the livingbody photometric apparatus is provided with an attachment member 40 forsecuring the ends of these optical fibers at predetermined positions.Herein below, the attachment member and the end portions of the opticalfibers secured to the attachment member will be called inclusively as aprobe 300.

The light source 10 is constituted by semiconductor lasers 11, whichrespectively emit light beams having a plurality of wavelengths (synonymof frequency) in a region from visible to near infrared, for example,wavelengths of 780 nm and 830 nm, a plurality of optical modules 12provided with modulators for modulating the light beams of the twowavelengths into a plurality of different frequencies and a plurality ofirradiation use optical fibers 13, which guide the light beams outputfrom the optical modules 12 to the probe. The light beams of the twofrequencies irradiated from the semiconductor lasers 11 are mixed andinput in respective optical modules 12 wherein the same are modulated indifferent frequencies in every optical modules, and the modulated lightbeams of the two frequencies are irradiated to the respectiveexamination portions of the subject via the respective irradiation useoptical fibers.

The optical measurement portion 20 is connected to detection use opticalfibers 21 and is constituted by photo-electric conversion elements suchas photo diodes 22 which convert the amount of the light beamstransmitted by the respective detection use optical fibers 21 torespective corresponding electrical signals, lock-in amplifier modules23 to which the electrical signals from the photo diodes 22 are inputand from which selectively output signals corresponding to respectiveirradiation positions and detection positions as well as the frequenciesand an A/D converter 24 which A/D converts the signals output from thelock-in amplifier modules 23. Number of lock-in amplifier modules 23 tobe provided is at least the same number of the signals to be measured.

The probe 300 is constituted in such a manner that a matrix of propersize such as 3×3 and 4×4 with a predetermined pitch is formed on theattachment member 40 and the ends of the irradiation use optical fibersand the ends of the detection use optical fibers alternatively disposedthereon by making use of a securing use socket.

The light beams detected by the detection use optical fibers in theliving body photometric apparatus are mixture of a plurality of lightbeams having different frequencies, which are respectively irradiatedfrom a plurality of adjacent irradiation use optical fibers and passedinside the living body. The lock-in amplifier modules 23 selectivelydetect these pluralities of signals having different frequencies withreference to the irradiation positions, irradiation frequencies anddetection positions thereof. Thereby, information inside the living bodyis detected at measurement points determined by points between the endpositions of the irradiation use optical fibers and the end position ofthe detection use optical fibers, more specifically, the intermediatepoints thereof.

These measurement points correspond to the number of channels detectedby the lock-in amplifier modules 23, for example, in a case of a probehaving 3×3 matrix, the number of measurement points between theirradiation positions and the detection positions is 12, thus a lightmeasurement of 12 channels can be performed.

The signal processing portion 30 is connected to the optical measurementportion 20 via a control portion (centralized processing unit: CPU) 31for controlling the entirety of the apparatus, processes the voltagesignals (digital signals) sent from the optical measurement portion 20and performs conversion thereof into signals representing living bodyinformation, more specifically, conversion into hemoglobin variationsignals representing hemoglobin density and variation thereof in time atthe measurement portions and preparation of data for topography image.Other than the above referred to image preparation function, the signalprocessing portion 30 includes such as a function of extracting from thehemoglobin variation signals measured at the respective measurementchannels signals (task related signals) representing a feature of a task(load) given to the subject at the time of the measurement and afunction of calculating based on the task related signals the mostreactive measurement portion (channel) with respect to the task. Inorder to perform these functions, the signal processing portion 30 isprovided with an arithmetic unit.

The CPU 31 controls such as operations of light beam irradiation anddetection, an application timing of the load (stimulus), processingincluding the analysis of the measured signals and preparation of imagesand display thereof. For this purpose a variety of softwares areassembled into the CPU 31. Further, the arithmetic function of-thesignal processing portion can be borne by the CPU 31.

The living body photometric apparatus is further provided with a memoryportion 32 in which digital signals sent from the optical measurementportion 20 and data of after signal processing are stored and an inputand output portion 33 which displays the processed result in the signalprocessing portion 30 as well as permits to input necessary instructionsfor the measurement and signal processing. More specifically, the inputand output portion 33 is provided with a input manipulation boardincluding on/off switches, key board and mouse and a display unit ofsuch as CRT and liquid crystal.

In the thus constituted living body photometric apparatus, the lightmeasurement is performed in such a manner that the light beams modulatedin different frequencies are irradiated from the probe 300 attached tothe living body through the irradiation use optical fibers 13, the lightbeams passed through the living body and detected by the detection useoptical fibers 21 are respectively converted into electrical signals,which are detected for every measurement point at an intermediate pointbetween respective irradiation positions and detection positions andhemoglobin variation signals are obtained by converting the electricalsignals into variation in time of the hemoglobin densities in blood atmeasurement portions. The hemoglobin variation signals measured at therespective measurement points are subjected to a variety of analysis inthe signal processing portion and these analysis results are displayedon the monitor screen in the input and output portion 33.

Now, an example of sequences for specifying a reactive portion of theliving body in response to a predetermined task in the above explainedliving body photometric apparatus will be explained with reference tothe flowchart in FIG. 2. The following explanation is a sequenceeffective for identifying a language area region in presurgicalexamination for epilepsy.

At first the probe is attached to the right and left temporal lobes ofthe subject (step 201). FIG. 3 shows the probe attached. As shown in thedrawing, in the present embodiment, the top ends of the irradiation useoptical fibers and the top ends of the detection use optical fibers arearranged in a matrix of 3×3. As has been explained previously, since themeasurement points are located at the intermediate points between thearranged points of the irradiation use optical fibers and the detectionuse optical fibers, the number of measurement points, namely, the numberof channels in the probe formed in the matrix of 3×3 of the presentembodiment is 12. Probes 301 and 302, each having 12 channel measurementpoints, are attached respectively to the right and left temporal lobes.Further, in FIG. 3, for example, 9 total optical fibers including 4irradiation use optical fibers and 5 detection use optical fibers arearranged at crossing points of the matrix in such a manner to sandwichthe positions indicated by measurement channel numbers. Accordingly, inthe case of the present embodiment in which the probe is attached to theright and left temporal lobes, 8 of the optical modules 12 and 8 of theirradiation use optical fibers 13 in the light source portion 10 and 10of the detection use optical fibers 21 and 10 of photo diodes in theoptical measurement portion 20 are required.

After completing the attachment of the probes 301 and 302 to the livingbody, the measurement is performed (step 202). The measurement begins toturn on a measurement switch provided at the input and output portion33. When turning on the measurement switch, the semiconductor lasers 11in the light source 10 are oscillated and emit light beams havingdifferent wavelengths of 780 nm and 830 nm, and the light beams havingthe two wavelengths are mixed and input into optical modules 12 a, . . .12 h, the two light beams having 780 nm and 830 nm input into respectiveoptical modules are modulated into different frequencies for everymodule by a modulator in respective optical modules. These modulatedlight beams are guided to the probes 301 and 302 via the irradiation useoptical fibers 13 a, . . . 13 h and are irradiated onto the right andleft temporal lobes. The irradiated light beams pass through the skinand the skull and after repeating passing and scattering of the lightbeams through the fine blood vessels and tissues in the brain, the lightbeams input into probe side openings for the detection use opticalfibers 21 a, 21 j. Further, since the light absorbance characteristicsof oxy hemoglobin and deoxy hemoglobin are different depending on thewavelength thereof irradiated from the irradiation use optical fibers,the light amount input from the detection use optical fibers differsdepending on amount of hemoglobin in blood vessels at the detectionportions. The light beams input into the detection use optical fibers 21a, . . . 21 j are respectively converted into electrical signals by thephoto diodes 22 a, . . . 22 j and these electrical signals arediscriminated according to the frequency thereof by the lock-inamplifier modules 23. Since the frequency of the light beams irradiatedfrom the irradiation use optical fibers corresponds to the positions ofthe optical fibers and the positional relationship between the detectionuse optical fibers and the irradiation use optical fibers aredetermined, the frequencies of the signals discriminated at the lock-inamplifier modules 23 and the measurement points are coordinated. Thenthe signals output from the lock-in amplifier modules 23 are convertedinto digital signals by the A/D converter 24 and output to the signalprocessing portion 30 in which signal processing such as for analysisand image display is performed.

The above measurement operation is performed while giving apredetermined task (stimulation) to the subject and the hemoglobinvariation signals are obtained from the subject. In the above example,since an identification of the language area is an object, stimulationsfor activating the language area such as a game of making word chainsand writing of words having a same pronunciation are given as the task.The task can be replaced by other stimulation to five senses to theliving body such as visual stimulation, olfactory stimulation, auditorystimulation and pain stimulation depending on the diagnosis object. Thenthe measurement is performed by combining an application period (loadingperiod) of the language stimulation and rest period (no load period) asa set and by repeating the set in plurality of times.

The hemoglobin signals appear as difference signals between the signalsmeasured under a condition when no load (stimulation) is given to thebrain of the subject and the signals measured after applying a load andone set of difference signals is obtained from the respective channel 1through 24 in the right and left probes 301 and 302 at the same time andis displayed. When the language stimulation is repeated, namely, aplurality set of hemoglobin variation signals are obtained in a timecourse, the latest information or averaging after adding the pluralityset of signals for respective channels is displayed.

FIG. 4 shows an example of displayed images on the monitor. As shown inthe drawing, the hemoglobin variation signal 401 is displayed in a timecourse graph for every channel wherein abscissa is time axis andordinate is hemoglobin density. In the graph, a stimulation start point(time) 402 and a stimulation end point (time) 403 are indicated on theordinate. Further, on the monitor screen a variety of command inputbuttons such as “Calc PCA” 404 and “Reference Graph” 405 are provided inorder to permit an operator to send a subsequent processing command tothe control portion 31 and the signal processing portion 30. These inputbuttons are always displayed on the following display screens.

The signal processing portion 30 performs a principal component analysisprocessing for the hemoglobin variation signals of the respectivechannels measured in step 202. The principal component analysisprocessing is a known method in the field of mathematics and in thepresent embodiment, a pattern having high abundance frequency withrespect to energy is extracted among the plurality of detected signals.In other words, some of representative signals having a contributionrate more than a predetermined contribution rate for the 24 channelhemoglobin signals measured are calculated (step 203). The principalcomponent analysis processing is executed by clicking the “Calc PCA”button 404 on the screen in FIG. 4. The principal component analysis isa method of converting high dimensional data into further lowdimensional data without losing information as much as possible and inthe present embodiment, as shown in FIG. 5, with regard to a pluralityof measured data of hemoglobin variation signals defined by axes of timeand channel number, the dimension (24 channels) of the channel axis iscompacted and is converted to data having further less channels.Further, when “Calc PCA” button 404 is clicked, the display screen ischanged over from one shown in FIG. 4 to one shown in FIG. 6.

The contribution rate is an index showing how much a principal component(representative signal) extracted via the principal component analysisexpresses the feature contained in the measured data and can bedetermined by calculating “a ratio of variance of the principalcomponent occupying in the total variance” in the principal componentanalysis. In the present embodiment, a representative signal having, forexample, more than 90% contribution rate is calculated.

An example of images displaying the result of the principal componentanalysis is shown in FIG. 6. As shown in the drawing, in the presentembodiment, two kinds of signals 601 and 602 are extracted and displayedas the representative signals. Since these two kinds of signals expressmore than 90% measurement data for all the channels, a third signal 603is not calculated.

When calculating the representative signals by compacting the measureddata with regard to the channel axis in the principal componentanalysis, coupling coefficients to be multiplied to the respectivechannels are calculated. These coupling coefficients are weights in therespective channels for the representative signals, namely, correspondto the abundance frequencies. Weights 607 and 608 for the respectivechannels calculated with respect to the representative signals 601 and602 are, for example, shown in a bar graph in which abscissa is thechannel number and ordinate is the weight and are displayed adjacent tothe representative signals. A relationship between actual signalsmeasured, representative signals and the weights will be explained, forexample, with reference to a eighth channel, in that an added value of avalue determined by multiplying the representative signal 601 with theweight for the eighth channel adjacent to the representative signal 601and a value determined by multiplying the representative signal 602 withthe weight for the eighth channel adjacent the representative signal 602is substantially the same as the actually measured value for the eighthchannel. Further, the weights displayed in the bar graph are effectivelyused by the operator for identifying the most reactive portion (channel)in response to the task.

Subsequently, the signal processing portion 30 correlates the calculatedrepresentative signals 601 and 602 with general hemoglobin variationsignals obtained in response to a given task, in that a languagestimulation and extracts a task related signal (step 205). The generalhemoglobin variation signal pattern with respect to the task is onedetermined empirically and experimentally by making use of othermodalities in the field of medical imaging diagnosis such as an MRIapparatus and a PET apparatus, and it is known, for example, that thehemoglobin variation in response to a language stimulation shows atrapezoidal pattern, in that rises in about 10 sec. from the start ofthe stimulation and decreases in about 10 sec. after ending thestimulation. When a task application pattern is fixed, these hemoglobinsignal variation patterns can be stored beforehand in the memory portion32, however, in the present embodiment, a case will be explained inwhich a user prepares a hemoglobin variation signal pattern with respectto a task in response to any application patterns to be set.

The preparation of the hemoglobin variation signal pattern is executedat the same time when, for example, by clicking “Reference Graph” buttonon the screen shown in FIG. 6, the displayed image as shown in FIG. 6 ischanged over to the one shown in FIG. 7 (step 204). FIG. 7 shows anexample of screen images when a user prepares a language reference andresponse waveform 701, which is a general hemoglobin variation signalpattern with respect to language stimulation. In this screen image, abox 705 is provided for inputting a delay time from the stimulationstart to the appearance of the maximum value of the hemoglobin variationand from the stimulation end to the return of the hemoglobin variationto the original state before the stimulation start, and when a delaytime in response to a load is input in the box 705, a trapezoidalwaveform having the delay time being input of, for example, 10 sec. isproduced as the language reference and response waveform 701 withrespect to a rectangular waveform having a signal value 1 at thestimulation start point 702 and the stimulation end point 703. Then, thelanguage reference and response waveform 701 thus produced is displayedby overlapping on the graph of the representative signals 601˜603 asshown in FIG. 6 (In FIG. 6, the language reference and response waveformis indicated as 605). Further, in the present embodiment, although anexample of inputting a numerical value for the delay time has beenshown, in another example, while assuming the rectangular waveformhaving signal value of 1 at the stimulation start point 702 and at thestimulation end point 703 as a figure, the delay time can be input bymoving the two apexes of the rectangular in the direction of the timeaxis by drugging operation of a mouse. Further, since it is sufficientif the step 204 of preparing the language reference and responsewaveform is executed prior to the step of calculating the correlationwith the representative signals, the preparation step can be performedeither before the start of the measurement or after the measurement.

The calculation result of the correlation between the representativesignals 601˜603 and the language reference and response waveform 701,namely, the correlation value is displayed together with the graph ofthe representative signals. In the display example as shown in FIG. 6,the correlation values are displayed at the right end portions of thegraphs of the representative signals as 611, 612 and 613. When observingthe display result, the correlation value between the representativesignal 601 and the language reference and response waveform 701 shows as0.88 and the correlation value between the representative signal 602 andthe language reference and response waveform 701 shows as 0.14,therefore, it is understood that among the two representative signalsthe representative signal 601 having a higher correlation value is thelanguage related signal. Further, in this instance, in order tofacilitate recognition that the representative signal 601 is thelanguage related signal, it can be possible after the correlation valuecalculation to change the color of the representative signal 601 havingthe highest correlation value, for example, in red and to display thesame. Thereby a user can recognize at a glance the language relatedsignal.

As has been already explained above, on the screen showing therepresentative signals 601, 602 and 603, for the respectiverepresentative signals, the calculation results of the weights of everychannel are displayed in bar graphs. Accordingly, after observing theweights for the respective channels corresponding to the representativesignal 601 serving as the language related signal, the operatorspecifies a channel having the highest weight (step 206). The channelhaving the highest weight corresponds to an active portion in the brainwhere responds most to the language task. In the illustrated example, itis understood that the eighth channel shows the highest weight. Thereby,it is diagnosed that the active portion in the brain where responds mostto the language task is at a position of the eighth channel on the lefttemporal lobe. With regard to the bar graph display of the weights, itis also possible to facilitate recognition if the color of the channelhaving the highest weight in bar graph is changed from that of the otherchannels, for example, the channel having the highest weight in bargraph is colored in red, alternatively, only the channel having thehighest weight in bar graph is displayed by inverting black and white.Further, it will be preferable to display an image showing an attachmentstate of the probe as shown in FIG. 3 in a window and to apply to theconcerned channel the above referred to recognizable indication. Stillfurther, these easy recognizable indications can be realized bysoftwares assembled in the control portion 31.

According to the present embodiment as has been explained, after beingdisplayed the hemoglobin variation signals measured (after step 202), byclicking “Calc PCA” button displayed on the same screen, since theextraction of the representative signals, the display of therepresentative signals and the weights and the display of the taskrelated signal determined from correlation with the predeterminedlanguage reference and response signal are performed, through observingthe weights of the respective channels for the task related signal, theactive portion where responds most to the task can easily identified.

Now, when identifying an active portion in the brain not being limitedto the identification of the language area region, it is sometimesnecessary to know which is dominance right hemisphere or lefthemisphere. The living body photometric apparatus according to thepresent embodiment can be provided with a function of determining suchhemispheric dominance.

A flowchart of determining the hemispheric dominance is shown in FIG. 8,in which steps 801˜805 are equivalent to the steps 201˜205 in FIG. 2.Namely, the probes are attached to the right and left temporal lobeswhere the language area exists (step 801), while giving a task to asubject under a predetermined condition, hemoglobin variation signals ofthe respective channels are measured (step 802). Subsequently, theprincipal component analysis is performed for the hemoglobin variationsignals of the respective channels, the representative signals arecalculated as well as inherent vector values of the respective channelscalculated through the principal component analysis are displayed asweights (abundance frequency) of the respective channels for therepresentative signals (step 803). Subsequently, for the representativesignals calculated in step 803, like FIG. 2 embodiment, a correlationwith the task reference and response waveform (produced at step 804),which is a typical response pattern to the task is calculated and thetask related signal is extracted (step 805).

When the task related signal (a representative signal having the highestcorrelation value calculated) is extracted in the above manner, averagevalues of the weights of every right and left channels for the taskrelated signals are determined. The average values thus determined aredisplayed, for example, as shown in FIG. 6, in numerical values at thebottom of the bar graphs showing the -weights of the respective channels(step 806). In the example as illustrated, the average value of theweights of the channels 1˜12 in the left hemisphere is 0.25 and theaverage value of the weights of the channels 112 in the right hemisphereis 0.125. Further, in the present example, although the average valuesof the weights of every channels are calculated, it is possible tocalculate and display such as average values of absolute value weights,average values of only positive symbol weights or negative symbolweights and average values of weights of above or below a predeterminedthreshold value.

The hemispheric dominance LI (Laterality Index) of right and left brainactivity can be calculated according to equation (1) by making use ofthe average values 614 and 615 of weights for right and left hemisphere.LI=(Al−Ar)/(Al+Ar)   (1)

Wherein, Al is the average value of weights for the left hemisphere andAr is the average value of the weights for the right hemisphere.

The above calculation according to equation (1) is performed either inthe signal processing portion 30 or in the control portion (CPU) 31 bymaking use of a software assembled therein.

The hemispheric dominance LI thus determined, although not illustrated,is displayed, for example, at the center of bar graphs of right and leftweights as shown in FIG. 6 as “LI=0.33”. This implies that Al>Ar inequation (1), namely, shows that the left hemisphere is dominant, and0.33 shows including “+” symbol. Oppositely, when Al<Ar in equation (1),it is indicated as “LI=−0.33” by adding “−” symbol to show that theright hemisphere is dominant. Further, the symbols “+” and “−” can beconverted into letters “left” and “right” through a software.

In the above explanation, the example in which the measurement wasperformed after attaching the probes to the right and left temporallobes and dominance of either the right or left hemisphere was judged,however, it is also possible to further divide the brain active regionand to measure the same and then to judge their dominance. Further, inthe above explanation, although the identification of language arearegion was primarily explained, it is also possible to identify regionsother than the language area, such as to identify a visual area bygiving a subject a visible stimulation as a task.

According to the present invention as has been explained hitherto,through extracting from the measured data only the activity signals inthe brain caused by the task (task related signal) and by specifying achannel having the highest correlation with the signal, thereby, theactive portion in the brain where responds most to the task can beidentified.

Further, according to the present invention, through displaying such asthe task related signals and the abundance frequency in the respectivechannels for the task related signals, a user can easily identifyvisually the active portion in the brain.

1. A living body photometric apparatus comprising: a light sourceportion for irradiating light beams having predetermined frequencies toa plurality of positions in a measurement region of a subject during aninterval including a period when giving a predetermined stimulation taskto the subject and a period not giving the same; an optical measurementportion for measuring light beams brought about by the irradiated lightbeams at a position near the light beam irradiation position and fordetermining measurement data at a plurality of measurement points fromthe measured light beams; a signal processing portion for calculatingfrom the plurality of measured data at least one stimulation task signalof which principal component is a signal brought about by thestimulation task given to the subject; and means for identifying ameasurement point or a region where responds most to the stimulationtask by making use of the at least one stimulation task signalcalculated by the signal processing portion.
 2. A living bodyphotometric apparatus comprising: a light source portion for irradiatinglight beams having predetermined frequencies to a plurality of positionsin a measurement region of a subject during an interval including aperiod when giving a predetermined stimulation task to the subject and aperiod not giving the same; an optical measurement portion for measuringlight beams brought about by the irradiated-light beams at a positionnear the light beam irradiation position and for determining measurementdata at a plurality of measurement points from the measured light beams;a signal processing portion for performing an imaging processing of themeasurement data from the optical measurement portion and forcalculating from the plurality of measured data at least one stimulationtask signal of which principal component is a signal brought about bythe stimulation task given to the subject; means for calculating anoccupying ratio of the plurality of respective measured data in thestimulation task signal; and a displaying means for displaying thestimulation task signal calculated and the calculated occupying ratio ofthe plurality of respective measured data in the stimulation tasksignal.
 3. A living body photometric apparatus according to claim 2,wherein the light source portion includes a light source for emitting aplurality of light beams having wavelengths near infrared region ofwhich absorbances with respect to oxy hemoglobin and deoxy hemoglobin inblood of a living body are different, optical modules for modulatingdifferently the wavelengths of the light beams emitted from the lightsource in the number corresponding to the irradiation positions andirradiation use optical fibers for transmitting the light beams outputfrom the optical modules onto a plurality of different positions of thesubject.
 4. A living body photometric apparatus according to claim 2,wherein the optical measurement portion includes a plurality ofdetection use optical fibers which are respectively disposed near theplurality of respective irradiation use optical fibers and guide andtransmit the light beams passed inside the subject, a plurality of photoelectric converting devices for converting the light beams transmittedby the respective detection use optical fibers into electrical signals,a signal separation and extraction circuit for determining measurementdata of the respective measurement points by making use of outputsignals of the plurality of photo electric converting devices.
 5. Aliving body photometric apparatus according to claim 2, wherein thestimulation task signal is displayed in a waveform defined by twocoordinate axes of signal intensity and time.
 6. A living bodyphotometric apparatus according to claim 5, further comprising means forgenerating a stimulation response and reference pattern in response tothe task stimulation of the living body and displaying the same on thedisplaying means while overlapping on the stimulation task signalwaveform.
 7. A living body photometric apparatus according to claim 6,wherein the stimulation response and reference pattern is stored in amemory means.
 8. A living body photometric apparatus according to claim6, wherein the stimulation response and reference pattern is determinedwhen an operator inputs through an input means data for modifying thepattern with respect to a preset pattern.
 9. A living body photometricapparatus according to claim 2, further comprising means for displayingoccupying ratios of the respective plurality of measurement datacalculated in the stimulation task signal.
 10. A living body photometricapparatus according to claim 9, further comprising means for displayinga measurement data having the maximum occupying ratio among theoccupying ratios of the respective plurality of measurement datacalculated in the stimulation task signal in a discriminable manner fromthe other measurement data.
 11. A living body photometric apparatusaccording to claim 9, further comprising means for calculating anaverage value after adding numerical values of the occupying ratios ofthe respective plurality of measurement data calculated in thestimulation task signal as well as for displaying the calculated averagevalue after the addition near the graph.
 12. A living body photometricapparatus according to claim 6, further comprising means for calculatinga correlation between the stimulation task signal and the stimulationresponse and reference pattern and for displaying the calculatedcorrelation value in numerical value near the display positions thereof.13. A living body photometric apparatus comprising: a light sourceportion for irradiating light beams having predetermined frequencies toa plurality of positions in a measurement region of a subject during aninterval including a period when giving a predetermined stimulation taskto the subject and a period not giving the same; an optical measurementportion for measuring light beams brought about by the irradiated lightbeams at a position near the light beam irradiation position and fordetermining measurement data at a plurality of measurement points fromthe measured light beams; a signal processing portion for performing animaging processing of the measurement data from the optical measurementportion, further for performing principal component analysis for theplurality of measured data and for extracting a representative signalwhich most reflects a living body reaction when the stimulation task isgiven; and a displaying means for displaying the signals processed and/or extracted by the signal processing portion.
 14. A living bodyphotometric apparatus comprising: a light source portion for irradiatinglight beams having predetermined frequencies to a plurality ofrespective positions in right and left temporal lobes of a subjectduring an interval including a period when giving a predeterminedstimulation task to the subject and a period not giving the same; anoptical measurement portion for measuring light beams brought about bythe irradiated light beams at a position near the light beam irradiationposition and for determining measurement data at a plurality ofmeasurement points from the measured light beams; a signal processingportion for performing an imaging processing of the measurement datafrom the optical measurement portion, further for performing principalcomponent analysis for the plurality of measured data and for extractinga representative signal which most reflects a living body reaction whenthe stimulation task is given; means for calculating contribution ratesof the respective measurement signals with respect the representativesignal; means for separating the calculated contribution rates of therespective measurement signals for the right and left temporal lobes andfor averaging thereof after adding the same; and a displaying means fordisplaying the averaged values after addition for the right and lefttemporal lobes determined by the averaging means after addition in adiscriminable manner.
 15. A living body photometric apparatus accordingto claim 14, further comprising a calculating means for calculatinghemisphere dominance representing which of right or left hemisphere inthe brain of the subject responds dominantly to the stimulation task bymaking use of the averaged values after addition for the right and lefttemporal lobes.
 16. A living body photometric apparatus according toclaim 15, further comprising means for displaying the hemisphericdominance determined by the calculation means on a display screen of thedisplaying means.
 17. A living body photometric apparatus according toclaim 16, wherein the discrimination of the right and left hemispheresis effected by symbols or letters and the degree of the hemisphericdominance is displayed by numerals.